1. Field of the Invention
The present invention relates to a rotary connection device to be used for electric connection between parts relatively rotatable with each other in automobiles, domestic electric appliances, or the like.
2. Description of the Related Art
As shown in FIG. 4, a steering wheel mounting part of an automobile is provided with a steering shaft 2 supported rotatably in a bracket 1 fixed on the body, and a switching device 3 and a rotary connection device 4 above the bracket 1. A steering wheel 6 is mounted on the tip end part of the steering shaft 2 projecting upward through the switching device 3 and the rotary connection device 4 so as to be rotated integrally with the shaft 2. Moreover, electric equipment 7 such as a horn switch and an air bag can be mounted on the steering wheel 6, as needed. The switching device 3 is, for example, an assembly of switches for a turn signal lamp, a wiper, or the like, with operation levers 8, 9 mounted on the right and left side surfaces thereof for a changeover operation of the switches.
As shown in an exploded view of FIG. 6, the rotary connection device comprises a flat cable (flexible flat cable . . . . FFC) 13 stored in a spirally wound state in a ring-like space 12 formed between a fixed side case 10 to be fixed on the body side, and a rotary side rotor 11 to be rotated integrally with the steering wheel 6 such that a connector 15 mounted on the other side end part of the flat cable 13 via an end member 15xe2x80x2 is connected with a connector 16 of the bracket 1 as well as a connector mounted on the inner side end part of the flat cable 13 via an end member 17xe2x80x2 is connected with a connector 18 of the electric equipment 7. The numeral 19 denotes a cover, 20 a C ring (stopper ring) for fixing the rotor 11 rotatably on the case 10, and 21 a smoothing sheet.
As shown in FIG. 5, in the rotary connection device after assembly, the rotor 11 can be rotated with respect to the case 10, with the inner circumferential surface part of the center hole part 10a of the case 10 and the outer circumferential surface part of the center axis part 11a of the rotor 11 serving as the rotational sliding part.
According to rightward or leftward rotation of the rotor 11 following a rotating operation of the steering wheel rightward or leftward, the flat cable 13 can be tightened or loosened with respect to the rotor 11.
However, due to friction between the surfaces facing with each other, a xe2x80x9cshoo, shooxe2x80x9d rotational sliding noise may be generated at the time of tightening or loosening the flat cable 13. In order to restrain such a rotational sliding noise, a flat cable 13 applied with a matte (like a satin finished surface having minute roughness) treatment on one surface for reducing the sliding friction has been proposed, however, it cannot restrain the rotational sliding noise satisfactorily.
The invention has been achieved for solving the conventional problem, and an object thereof is to provide a rotary connection device capable of effectively restraining the rotational sliding noise of a flat cable.
In order to solve the problems, the invention provides a rotary connection device comprising a fixed side case, a rotary side rotor rotatable in the case, and a flat cable stored in a spirally wound state in a ring-like space part formed between the case and the rotor, wherein a film of a solid lubricant is coated on both sides or one side of the flat cable.
According to the invention, since a film of a solid lubricant is coated on both sides or one side of the flat cable, only the film and the surface facing thereto, or the films slide with each other at the time of tightening or loosening the flat cable, and thus the sliding friction can be reduced drastically at the time of rotational sliding.
The film coating operation with the solid lubricant can be executed in either the flat cable operation or the flat cable assembly.
Moreover, the film of the solid lubricant is preferably a fluorine based film, but can be a molybdenum based film, or a silicon based film.